The dates of commerce are the fruit of the species of palm, Phoenix dactylifera. Another species, Phoenix sylvestis, which is very closely related to the date palm, also produces dates. Dates are known to contain high amounts of sugars, amounts ranging as high as 50% to 60% by weight.
In the past, some sugar has been recovered from dates by pressing the fruit to release some of the sugars in their natural liquids. Pressing, however, is not a commercially viable process for a number of reasons. Pressing breaks down the hemicellulose walls and releases impurities which are difficult, and expensive, to separate in a commercial operation. Moreover, pressing only recovers a fraction of the large amounts of the sugars available in dates.
Although dates are known to contain large amounts of sugars, the extraction of their sugars has formidable obstacles which have prevented their recovery on a commercial scale. The skins and the cell membranes of dates are tough, and the fruit has a gummy consistency, so that they are not easily broken and subdivided, in order to extract the sugars efficiently.
Dates are known to contain three sugars: fructose, sucrose and glucose. In the past, attempts to extract sucrose, fructose and glucose from plant materials simultaneously has not been commercially successful. It has been the custom in the extraction and purification of sucrose to single out sucrose individually, and to treat the fructose and glucose as impurities, and not to recover them. In plants containing a high percentage of fructose, it has been difficult to recover the fructose singularly, because of other impurities. Thus, plants containing a predominance of fructose, such as oranges or grapes, are sold without processing them for supplying the fructose for human consumption. In the case of grapes, the fructose is processed into alcohol for a greater financial return. As a result, fructose is generally produced from plants high in carbohydrates, like corn, where the carbohydrate (i.e., starch of the corn) is converted enzymatically, or by some other means, to fructose.
Glucose is often produced as a by-product in the chemical or enzymatic processing for fructose, and is often included with the fructose in liquid sugars. Sucrose is sometimes chemically or enzymatically converted to fructose and glucose to produce liquid sugars.
Liquid sugars containing sucrose, fructose and glucose naturally blended have not been available commercially heretofore. Dates are unique in not only containing these three sugars blended together in the natural state, but also in having these sugars present in high quantities. The relative amounts of these three sugars in dates varies with the region in which they are produced. For example, dates from Algeria contain fructose in the largest proportion, whereas dates from Southern California contain sucrose in the largest proportion of the three sugars.
As indicated above, dates are difficult to comminute, as by grinding, pulverizing, chopping or slicing, because of their tough skin and cell walls, and their gummy consistency. For this reason, they are most often sold and used as articles of commerce as the intact fruit, pitted, or unpitted. The several other parts of dates, however, also may yield products of value to the area where they are grown. The seeds, or pits, for example, are sometimes ground and used for feed stock. The stems of a small species Phoenix farinifera are sometimes processed to make a date palm meal.